The Channel 4 Sitcom Festival 1999

I have always avoided living with strangers," says comedian Gina Ryan. "Once, a flatmate and I had to interview people to share with and it was just like Shallow Grave, with all these freaks turning up. One bloke was a ginger-haired cyclist, so we wanted him out straight away." Virtually every Londoner has known the pleasure and misery of flat-sharing at some time, so it is perhaps no surprise that it provides the theme for a couple of the half-hour shows in the Channel 4 Sitcom Festival, an annual showcase for wannabe comedy scriptwriters.

Ryan, 33, makes her debut with Ladies of The House, a tale of three "totally inappropriate" female New Labour MPs who find themselves cohabiting in a luxury Kensington pad. Meanwhile, Stephen Powell, 36, has written a flatshare drama with a difference: Tooled Up is set in a cell at Brixton Prison, with four bunk beds replacing the usual cosy sofa.

"It is the flatshare from hell," he agrees, during a break in rehearsals at Hammersmith's Riverside Studios. "It's also an enforced flatshare. Most are, and most are also based on economic decisions - as ending up in prison often is."

Powell, who directed Brixton inmates in a production of Hamlet some years ago, drew his inspiration from the antics of his father, a former East End petty criminal who has been in and out of prison.

"He first got sent away for throwing a brick at a cigarette machine," says Powell. "It was all grist to the mill, because you learn how to be a criminal in prison, and he was in there on and off until he was 17. He's been back for various things over the years, but he's sort of grown out of it. We've started to talk about it all over the last couple of years. He had always described things as sounding quite glamorous, but then he started saying how he wished he had not spent all those years away."

"He's actually quite a civilised bloke, and well read, because he had to educate himself. He likes showjumping and sailing, and he's a real raconteur, with lots of charm."

Powell Snr is long familiar with his son's drama - after its premiere in London, during which he clutched his head in his hands in embarrassment, he held court in the audience, whisky and cigarette in hand, lapping up the attention.

Tooled Up then went on a successful Edinburgh run last year as a one-man show. The Channel 4 version may attract comparisons with Porridge, but Powell thinks the surreal dialogue has more in common with Black Adder. "I would be very flattered if it were compared with Porridge, but I think our ideas of prison have changed since then," he says. Beneath the comedy there's a serious message. "The greatest crimes in this country are being black and poor - or thick," he says. "The prison service should be in the hands of the criminal justice system, not the Government. Like education, it's too important and dangerous to be in the hands of political expediency."

Gina Ryan, a successful comedy circuit stand-up, has also injected some bite to her sitcom, which reflects a post-honeymoon disillusionment with the new Blairite MPs who were swept into Parliament.

"I don't think these people have done anything wrong, because they are not allowed to," she says. "No dissenting voices are allowed. I find it really scary and disturbing. I would not get involved with a political party now because it is too careerist - there's no integrity involved."

Even the climate for political comedy seems to have changed. "If you try to do something direct about political issues now, audiences tend to switch off," she sighs. "Everyone is a bit fed up. The Government is not supposed to be the enemy, but it is. People are disappointed but feel they can't show it."

Her characters include "a Melinda Messenger, Channel 5 celebrity type who is actually really brilliant but has created herself as a bimbo out of ambition". Sharing her sofa are a naive, but well-meaning, country woman who has been propelled to Westminster as a heroine of the green protest movement, and a woman who has won her seat to spite her MP husband for running off with his secretary. "She is based on my stand-up character - the bitter, nasty person. It's only when I hear someone else saying the lines that I realise how truly nasty I am."

The script is not finished yet. "I couldn't do a thing last night because there was a mouse in the flat and I was just crying all evening." It could be worse. You don't get ginger-haired mice, after all.